IRS Cage mounts (on car)

If you’re going to let a washer in, then sure that would work.

The only connection between the IRS mounts and your chassis is by these bolts. The bolts and the tubes are taking the beating. Me thinks it is important to have a snug a fit as snug can be. As soon as slop is introduced wouldn‘t movement start clunks? The rubber takes the movement, the bolts take the loads up/down and sideways. (Hence important to have the side shims where appropiate.) Front/aft as well, but is also taken by the trailing arms.

If a washer either end is all that is supporting the weight, it’s really not that much better than having no tube at all, in my opinion. I’d be going for a 5/16" ID tube. It does seem difficult to find though, for some reason. Quite a few suppliers have 5/16" ID, 5/8" OD steel tubing, but that seems a bit of overkill. Most of the 5/16" ID stuff seems to be stainless. McMaster-Carr does have some 3/8" or 7/16" OD stuff with 5/16"+ ID.

By “let in” I meant large holes bored in the leg, the washers welded to the tube, then the whole “H” tube welded into the leg.

If welded properly this would be as strong as the original. (stronger if the OD of the tube was larger.

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True enough. I was referencing Geoff’s post above (#8) where he mentioned he used the washers and a tube to make his repair.

Any idea what the OD of these tubes is?

The OD should not matter at all. The only important consideration is that the bolts fit well into the tube, the tube is located correctly, and that the welding is done well. A thicker tube is probably an advantage as long as it is not so thick that it fouls against the side of the chassis leg. Just use large washers and drill them out to the tube OD.

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For clarification. The washers are welded to the chassis legs AND the tubes.

are the washers going to be flush with the chassis leg?

No the washers take up the space formerly occupied by the shims. However if you wanted to get really fancy you could weld them in flush with the chassis legs. That would require much more precision and better welding skills though.

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that’s why I was asking, my car at that position only had one shim outer. A washer is much thicker than one of those shims.

There was lots of room on mine. I was installing new mounts at the time though. Perhaps whoever installed your mounts had tightened down the throughbolt enough to crush the mount down in width?

No. I was installing new ones and I just barely got the same shims back in the same places throughout.

what’s the purpose of the shims anyway?? Why not build the hangers to fit the frame snugly? Do the shims allow for a wee bit of adjustment of placement?

I think if they didn’t leave the shim space it would be even more fun trying to install the cage.

But yeah, I think there must be some other arrangement they could have designed.

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Yes, to the second, and the first would take a MUCH higher level of build precision, one that Jaguar simply did not possess.

I believe these bolts are not in a shear capacity. The mount does not “hang” on the bolts. The bolts clamp the mount to the frame rail. The mount is then held in position by the friction between the mount, any shims, and the frame rail, the same as most bolted connections. In theory, the bolt would not ever have to touch the tube. The tube prevents crushing.
Tom

Back to your original question Tom. Have you decided how you will fix your torn chassis leg?

Well, if they weren’t present you’d have pinched mounts as opposed to clearance once the shims are removed. The loose fit facilitates offering up the irs.

Re: your collapsed mounting boss. You might consider drilling out the spots and repairing on the bench as it’s a sub assembly of the chassis leg. Martin Robey provides all sorts of parts not listed and can probably purchase one though repairing yours might be better.

Thanks Doug—one thought—I install the hangers before “offering up” the IRS. /that way I only have the one bolt on the hanger to worry about lining up.

tom